ENDODERM
Endoderm is the innermost germ layer in the developing embryo. The development of endoderm from undifferentiated blastula cells requires a fantastic interplay of gene expression.
Scientists have identified many strategies to induce differentiation of embryonic stem cells in vitro. By studying embryonic stem cells in vitro, scientists now recognize some of the mechanisms by which endodermal cells give rise to mature structures, and the differentiation of hepatic cells and pancreatic cells, which share a common embryonic origin, has been studied extensively.
GENES INVOLVED
IN ENDODERM DEVELOPMENT
What genes are involved in the development of endoderm?
The main players in endodermal development include the Sox genes, Mixer, and Vg1. The Sox genes were once thought to be the key regulatory players in the differentiation of endoderm. In 1998, the gene Mixer was identified in Xenopus laevis as another key gene for vertebrate endoderm development (11). Mixer induces expression of the Sox17 genes, but the Sox17 genes do not play a role in the induction of Mixer. Mixer is induced only at high levels of Vg1 gene expression, and Xbra (a gene required for mesodermal induction) is signaled at low levels of Vg1 expression. In this way, Vg1 determines whether a cell will have a mesodermal or endodermal fate (11).
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